This invention relates generally to methods, instrumentation and devices for use in a surgical procedure for the repair of bone fractures and the fixation of orthopedic implants. More particularly, this invention relates to methods, instrumentation and devices for securing an orthopedic implant, such as a bone fracture reduction rod, intramedullary nail, or other prosthetic device. This invention even more particularly relates to an improved orthopedic screw with an enlarged shank diameter at the trailing end of the screw and an internal capture surface recessed into the head and at least part of the trailing end, along with a driver capable of engaging the internal capture of the screw.
Surgeons perform a variety of orthopedic procedures requiring screws specifically designed for use in bone tissue. A wide array of bone screws exist which are adapted to perform specific functions or to be compatible with a specific type of bone tissue or orthopedic implant.
For example, in order to stay a bone fracture, particularly in a long bone, a surgeon may insert a bone fracture reduction rod, or intramedullary nail, into an intramedullary canal of the bone. In order to secure the rod, the surgeon will place bone screws through holes in the intramedullary nails. Screws used for this purpose often extend through the bone and the hole in the nail and into the far cortex on the opposite side of the long bone. The use of such screws provides many advantages such as increasing the rotational stability of the implanted nail, enhancing the union rate of the bone, and promoting limb rehabilitation.
However, the use of such bone screws also presents certain challenges. For example, a surgeon often needs to have several drivers available during a procedure because a single nailing system typically employs a large number of different screws of various sizes. As a result, the surgeon may be required to exchange drivers in the middle of the procedure. Moreover, bone screws which are not secured to the driver during implantation can slip off and become lost within surrounding muscle tissue. Retrieval of these screws proves difficult when the bone area is surrounded by a large amount of soft tissue, such as in the areas adjacent the forearm and the proximal thigh, particularly in larger patients. The delay in retrieving the lost screw and other inconveniences and risks associated with the loss of screws during surgery are not only unnecessary, but can compromise the success of the procedure.
Therefore, in performing orthopedic surgery it is desirable for the bone screw to be coupled to a driver to allow attachment of the screw to the driver prior to implantation in the bone, in order to avoid losing the screw in the surrounding soft tissue during the procedure, and to allow release of the screw in a desired manner after implantation. Screw and driver combinations exist which allow axial attachment of the screw to a driver prior to insertion, after which the surgeon rotates the driver until the screw is fully implanted. After implantation, the driver is disengaged from the screw. However, although known screw and driver combinations help reduce the risk of screw loss, these previous capture mechanisms typically suffer from one or more problems which limit their utility and performance.
For instance, prior art screw and driver combinations exist which utilize an external capture mechanism, such as a geometrically shaped head for engaging a driver with a socket for receiving the shaped head. However, these mechanisms proved undesirable due to irritation of the surrounding soft tissue caused by the bulky heads. Additionally, often a surgeon desires to countersink the head of the screw into the bone so that the top of the head is flush with or beneath the bone surface to further avoid tissue irritation, but the heads of the external capture screws can not be appropriately countersunk. Other external capture mechanisms include drivers with chalk-holder type devices for grasping the head of the screw during implantation. Screws with smooth, rounded heads, which cause less tissue irritation, can be used with such drivers; however, the use of a chalk-holder type mechanism does not allow for a tight seating of the head against the bone and also prevents countersinking of the screw head within the bone.
Prior art screw and driver combinations also exist which possess internal driving mechanisms, such as an internal hex socket for receiving a corresponding driver. However, these screws merely allow for proper seating and countersinking of the screw head or top end of headless screws, but do not provide an internal capture surface for securing the screw to the driver prior to insertion in the bone in a manner that allows the screw to stay positioned on the driver during manipulation, yet be released when desired.
Some such screws additionally include an axial cannulation through the length of the screw body through which a guide wire is threaded to both guide the screw to the insertion sight and allow retrieval of the screw if lost prior to or during insertion, such as screws with an internal driving surface and a cannulated design. The guide wire method allows for re-capture of a lost screw but does not prevent the initial loss of the screw due to disengagement from the driver during insertion.
Prior art screw and driver combinations which provide for internal capture of the screw prior to insertion often do not allow sufficiently rigid capture of the screw to the driver to prevent movement of the screw relative to the driver during insertion, and such screws frequently possess other serious structural and functional problems. For instance, prior art screws having one or both of an internal capture surface and internal driving surface are disadvantageous in that the creation of the socket, enlarged bore, or other recession into the head and upper portion of the screw shank reduces the structural soundness and weakens the fatigue strength of the screw, which may result in breaking of the head or upper portion of the shank.
Accordingly, what is needed is an orthopedic screw with an internal capture surface capable of rigidly engaging a driver prior to and during insertion of the screw in a patient yet releasing from the driver when desired, while simultaneously maintaining structural soundness and adequate fatigue and head break strength. Also needed is a driver designed to correspond to the internal capture and driving mechanism of the screw, and methods of implanting and using the screw. Further, what is needed is a system for use in a procedure for the fixation of an orthopedic implant in a patient that includes an orthopedic implant and screws with an internal capture surface and adequate strength which are adapted to secure the implant to the skeletal system of a patient.
Methods, devices and instrumentation of this invention seek to provide an orthopedic retaining device capable of being rigidly coupled to an insertion tool while maintaining structural and functional integrity of the retaining device and capable of being released from the insertion tool after insertion. Rigid internal capture is possible without compromising the strength of the retaining device and while avoiding irritation to surrounding tissue.
Methods, devices and instrumentation according to this invention more particularly provide an orthopedic screw, an orthopedic screw and driver assembly, a system employing the orthopedic screw for the fixation of orthopedic implants, and methods of using the screw, assembly, and system that provide adequate capture of an orthopedic screw to avoid loss of the screw during implantation, while also maintaining adequate structural and functional integrity of the screw. These and other aspects of the orthopedic screw, assembly, and system of this invention make them easier and more practical to use than prior art orthopedic screws, assemblies, and systems.
One orthopedic screw according to this invention includes a head, an internal capture surface, and a shank extending from the screw head to a distal tip. The screw shank has an enlarged diameter at the trailing end, in the area just under the head of the screw, in order to accommodate the internal capture surface without sacrificing the strength or structural soundness of the screw. The screw also includes a continuous thread along at least a portion of the shank extending radially outward from the shank. The enlarged diameter of the trailing end of the shank of a screw according to this invention provides adequate strength and better purchase of the bone material.
The internal capture surface of the screw allows the screw to be securely attached to a driver prior to insertion of the screw into the bone and released from the driver after insertion, which avoids the loss of the screw in the soft tissue of the patient during the procedure. The enlarged diameter of the trailing end provides structural reinforcement in the area of the shank below the head in order to compensate for strength lost due to the recession of the capture mechanism into the head and upper body of the screw.
One screw assembly according to this invention includes an orthopedic screw, as described above, in combination with a driver having a driving member adapted to engage the internal capture surface of the screw, and a locking member adapted to engage the internal capture surface of the screw to secure the screw to the driver.
An additional aspect of this invention is an system for use in fixing an orthopedic implant in a patient. Such a system includes screws of this invention and an orthopedic implant, such as an intramedullary nail or fracture reduction rod, an orthopedic plate, external fixture, tibia base, or acetabular shell, which can be secured to the skeletal system of a patient using an orthopedic screw according to this invention.
Another aspect of this invention also seeks to provide a method of using the orthopedic screw assembly for manipulating a screw in bone material without a significant risk of losing the screw. Another aspect of this invention provides a method of using the orthopedic screw and screw assembly for repairing a bone fracture or for fixing an orthopedic implant in a patient.
The screws and screw assemblies of the present invention provide many benefits and advantages. One feature according to one aspect of this invention is the ability to safely drill a bone screw with a variety of drivers including power and hand drivers.
Another feature of another aspect of this invention is a bone screw that will not cause significant irritation to adjacent soft tissue and that is adapted for countersinking into the bone.
Another feature of an aspect of this invention is a bone screw with an internal capture surface without a corresponding reduction in screw strength or integrity. The screw is structurally sound and is at least equivalent in strength to bone screws without internal capture surfaces which are currently on the market.
Yet another feature of an aspect of this invention is an orthopedic screw assembly that securely retains a screw to a driver prior to and during insertion of the screw into a bone to avoid loss of the screw in surrounding soft tissue.
Another feature of an aspect of this invention is the ability to easily release the screw from the driver after insertion into the patient.
These and other features of this invention will become apparent after a review of the following detailed description of the disclosed embodiments.